Resolve or reject a deferred or promise multiple times

[sight...@gmail.com]

Hey guys. At first thank you for this awesome piece of work. DeftJs solved so many issues i had with vanilla extjs architecture.

My question is: Is it possible to resolve or reject a deferred/promise multiple times, so the registered callbacks gets called multiple times?

Thx in advance.

ExtJs-Version: 4.2.0

DeftJs-Version: 0.9.1 (stable i think)

[Brian Kotek]

I'm fairly sure that if you call when()/then()/finally() on a Promise that is already resolved (or rejected) it will immediately trigger any chained Promises or callbacks.

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[Brian Kotek]

Hmm but to add, if you're asking if you can actually call resolve() or reject() again on a Promise that is already resolved or rejected, I'm not sure (just because I've never done it). My *guess* is that it would trigger the callbacks, but you'd want to double check to be sure.

[John Yanarella]

Great to hear Deft JS has been useful for you!

No, by design a Promise can only resolve / reject once.

A Promise represents a future value (i.e. a value that may not yet be available). Just one value, though. Not subsequent changes to that value. Promises are not intended to be a general purpose notification system like events, signals, or streams.

Check out Domenic’s presentation to the NY Times on Promises for some discussion on this: 

* Slides: http://www.slideshare.net/domenicdenicola/promises-promises

* Video: http://www.youtube.com/watch?v=MNxnHbyzhuo

In terms of the primitives offered by the Ext JS framework, you may want to create an instance of Observable (an event bus) and attach callbacks to that.  There are also many third party (non Ext JS specific) JS libraries available that offer nice implementations of signals and streams.

Best regards,

-J